1965 Valiant low brake pressure

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Mrpatatomoto

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Okay, heres what I need help with. I have a 65 Valiant that stopped better than our new cars, Manual 4 wheel drum brakes. The MC went out so we bought a new one and replaced it and the brakes worked fine for a couple days. Then as old cars typicaly go the added pressure of the new MC blew the seals in the front wheel cylinders (first the left then noticed the right leaking when I was changing the pads on that side). Since I put new wheel cylinders on I have had almost no brake pressure, the car will stop if I hit the brakes really hard but thats shouldnt be necissary. I have adjusted the adjusters to the point of not being able to turn the wheel and backed off to where is barely rubs on all 4 wheels (figured I might as well adjust the back while I had it in the air). I have went through almost two of the large bottles of brake fluid bleeding the system. Ive even gone as far as exchanging the master cylinder for another one incase that one was faulty (An old book of my dads said that it should squirt fluid up on the back stroke and it was doing it on the forward stroke, the new one does it correctly). I feel like im leaving something out that I tried but its been a long week under that car. Any help/suggestions would be much appreciated. OH, there are no leaks in the system that I can find and all the rubber hoses look good.

Thanks in advance,
Mike
 
So what are you saying here? You have a full pedal but it takes a lot of effort to stop the car?
 
oldkimmer said:
...........u have adj the brakes too low.............just back them off so u the turn the wheel ..........kim.........
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Thats where I had them origionally but when I took it for a test drive when I let off the gas I could feel excessive drag so I adjusted them off a little more. And when they were origionally tighter the pedal was about the same as it is now.

Mike.
 
OK, lets start with the basics just to make sure we dont chase something simple for days. Are you sure it is a drum/drum MC and not a disc/drum? ( no, I dont doubt your intelligence but i do doubt the intelligence of autozone employees). did you bench bleed the MC before you hooked it to the rest of the system? did you start bleeding from the farthest wheel from the MC? are the bleeder screws all in all the way? (not just tight, one might have gotten stuck part way allowing air in)

and did you wait for all the little air bubbles to stop coming up from the MC?
 
Bmsjax said:
OK, lets start with the basics just to make sure we dont chase something simple for days. Are you sure it is a drum/drum MC and not a disc/drum? ( no, I dont doubt your intelligence but i do doubt the intelligence of autozone employees). did you bench bleed the MC before you hooked it to the rest of the system? did you start bleeding from the farthest wheel from the MC? are the bleeder screws all in all the way? (not just tight, one might have gotten stuck part way allowing air in)

and did you wait for all the little air bubbles to stop coming up from the MC?
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Is there a way to tell if it is a disk/drum or a drum/drum? I usually read the screen when they are looking up parts and it was under 4 wheel drum, but that doesnt mean it wasnt packaged wrong. Yes I bled the MC before putting it on (didnt on the first one which could be why it was defective) Yes bled RR>LR>RF>LF and the bleeder screws do stick out a little bit more than I expected but before I put them on I tried screwing them in and that seems to be as far as they go in. and they are the same with both the new ones so I assume thats just how they are supposed to be. Yes I waited for all the bubbles to be gone before bleeding.

To Chryslerfat, The hose goes to the WC below the bleeder valve.



Thanks,
Mike
 
Ok did they possibly give you the incorrect bore cylinders? I know there is a difference between what is on the 9 inch compared to the 10 inch brakes.
 
chryslerfat said:
Ok did they possibly give you the incorrect bore cylinders? I know there is a difference between what is on the 9 inch compared to the 10 inch brakes.
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No, I measured wrong and got the 10 inch ones the first time and it didnt fit at all, so the wheel cylinders are 9 inch for the 9 inch drums.

Mike
 
drum/drum will have the same size bowls or one common bowl and disc/drums should have a smaller bowl towards the front of the car. Disc requires less fluid movement to engage then drums.
 
Sounds like you got a master cylinder that had been sittin on the shelf a while. Sounds like the master cylinder is leakin internally. This is why I always rebuild mine. I have learned too many times the hard way.
 
Are the pins held in the rubber boots properly so they dont move and cause the pistons in the cylinders to move farther than necessary?
 
Mrpatatomoto said:
Single
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Ok, i would recommend a dual, split line system upgrade. Safer and works ALOT better. Did it on a '64 Chevy pick up and was surprised in the difference it made. And not too hard to do.

Until then:
Next I would check that you have enough freeplay in your pedal. If your pedal doesnt come back enough to clear the ports inside your MC you'll never create pressure. And check the pedal rod that goes into the MC. I once had a replacement MC that had a shorter length hole than the original and I had to cut down the brake rod.
 
Well its a single bowl so from what you say all it can be is Drum/Drum since disk would require tis own bowl.

They did say it was coming from the warehouse, but if it was leaking internally wouldnt the pedal sink to the floor when I hold it down instead of sitting at a static point?

What pins in what rubber boots? the wheel cylinder? I didnt look at them at all before putting them on just put it all together. But they were brand new(or atleast reman's) so I assume the pins are where they are supposed to be.
 
Bmsjax said:
Ok, i would recommend a dual, split line system upgrade. Safer and works ALOT better. Did it on a '64 Chevy pick up and was surprised in the difference it made. And not too hard to do.

Until then:
Next I would check that you have enough freeplay in your pedal. If your pedal doesnt come back enough to clear the ports inside your MC you'll never create pressure. And check the pedal rod that goes into the MC. I once had a replacement MC that had a shorter length hole than the original and I had to cut down the brake rod.
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Thats is one problem ive been having, it doesnt come all the way back and Ive had to keep adjusting the brake light switch so the lights turn off, so if I rig a spring or something in there to pull the pedal all the way up would it fix the probem at all? I know its supposed to return by pressure, but its not doing that. Or would just pulling the pedal all the way up and pumping a few times fix the problem? I also held the two MC's nect to eachother and made sure everything was the same size, so the shaft isnt the issue.
 
Not necessarily. You said it was fine for a while and then went all to hell. If everything else is right....which is tough to tell because of the now chinese wheel cylinders, the master cylinder is the only culprit. This is exactly why I say rebuild rebuild rebuild. That way, you know you have the correct cylinders. Only a couple of times have i ever not been able to rebuild a master of wheel cylinder or caliper. Plus, it's way more cost effective.
 
First off, my last post said something about a mod needing to see it before it would post, im not sure why its doing that.

The first replacement MC worked right till the wheel cylinder went out and since then I havent got the pressure back. So I assume its the correct one. Which makes me wonder if theres something wrong with the WC's but they are pretty basic and that I know of if theres no fluid coming out of them and they do move when you press the barkes theres nothing else to be wrong with them. Other than wrong size which im 99% sure they are correct.
 
I don't know if this will help since it's a bit of a different system. When I worked on air cooled VW's they didn't have self adjusting brakes (there was actually a good reason for this, but I won't get into that now), so you had to adjust them on a regular basis. If you just adjusted them until the shoes dragged & then backed them off a bit you'd end up with too much free play in the pedal. If I remember right, the trick was to adjust them until the shoes dragged, then stomp on the pedal hard several times. This centered the shoes a bit in the drum & gave you some more room to adjust them. After a couple of times of doing this then backing the adjuster a couple of notches at each wheel you would still have a good pedal when you were done. Might be worth a try.
 
Yes a internal leak in the MC will almost always result in a pedal that gets lower as you hold it.
Again I suggest next checking your pedal free play. I dont know how '65 are but on my '70 there is a bolt you loosen on the bracket for the brake switch to move it back and forth for adjustment. Loosen it and allow the pedal to come all the way back and then test for pressure then adjust the bracket to the new pedal height.
I think your WC are fine(unless they are Autozone 'brakeware' brand)
 
'64 Cuda said:
I don't know if this will help since it's a bit of a different system. When I worked on air cooled VW's they didn't have self adjusting brakes (there was actually a good reason for this, but I won't get into that now), so you had to adjust them on a regular basis. If you just adjusted them until the shoes dragged & then backed them off a bit you'd end up with too much free play in the pedal. If I remember right, the trick was to adjust them until the shoes dragged, then stomp on the pedal hard several times. This centered the shoes a bit in the drum & gave you some more room to adjust them. After a couple of times of doing this then backing the adjuster a couple of notches at each wheel you would still have a good pedal when you were done. Might be worth a try.
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I second that this is a worth a try as well
 
Some basics:

The two big reasons for a LOW pedal are loose brake adjustment or air, which should result in a soft low pedal

When you adjust shoes, adjust them up "no can turn" and back them off. This will center/ seat the shoes

The master piston "may be wrong one" must have the correct stroke to "not" have too much free play, yet allow the piston to come back past the port in the master. Easily seen by fluid squirting back in the return, easily felt with a finger or two on the pedal "feeling" for free play/ start of stroke.

On older systems, (single) they should ALL have a "residual pressure valve" and in those masters, they look like a "salt shaker" lid in the end of the master --far end of the piston return spring, and usually the "first thing in"

Make sure your wheel cylinders AND the master are the same / correct bore size

Since you are having a low pedal problem, I would tighten up all wheel adjustments until the wheels won't turn, then bleed the brakes and VERIFY that you have a very high, very firm pedal at that point. Then back off the adjustments until they drag. At this point as suggested above, "stomp" the pedal to recheck adjustment/ seat the shoes. Most brakes will still scrape after adjustment for awhile. In other words, do not back them off too far.
 
Ok back to the problem that you lost the pedal after wheel cylinder replacement. When you changed them there are pins that go in the rubber cups and push against the shoes. Did you transfer them to the new cylinders? and make sure they are bottomed in the shoe because as I said earlier if they have travel to apply your pedal has travel. Again what people are failing to read here is he was ok till the cylinders were changed so most likely that is where the problem lies.
 
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